Continuous process for thermal splitting of carbamic acid esters

US4692550A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Theodor Engbert · Recklinghausen, DE
• Gunter Hammen · Dormagen, DE
• Hartmut Knofel · Odenthal, DE
• Klaus Konig · Leverkusen, DE

Key dates

• Filing date: Apr 15, 1983
• Grant date: Sep 8, 1987
• Expiry date: Apr 15, 2003

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C263/04
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

N-monosubstituted carbamic acid esters are thermally split on a continuous basis in a tube reactor. The carbamic acid ester which is flowed down or passed over the inner wall of a tube reactor is thermally split at a temperature of from 150.degree. to 450.degree. C. and under a pressure of from 0.001 to 20 bar into at least two fractions. One fraction is predominantly isocyanate and a second fraction is predominantly hydroxyl compound. These fractions may be separated by removing one as a gaseous fraction formed under the splitting conditions from the head of the reactor and collecting the second fraction as a liquid which accumulates at the base of the reactor. If both fractions are gaseous under the splitting conditions, they are both removed from the head of the reactor and subsequently separated by fractionating columns for example. This process is particularly advantageous in that isocyanate and hydroxyl fractions are obtained in high yield without using a solvent.